Method of normalizing coiled springs by a high-frequency magnetic field



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J. L. CALLEY METHOD OF NORMALIZING COILED SPRINGS Filed Sept. 25, 1944 I I I I I S \\\\\\\\\\\\\\\\\\\\\\\\\\\\s BY A HIGH-FREQUENCY MAGNETIC FIELD Dec. 6, 1949 Patented Dec. 6, 1949 METHOD OF NORMALIZING COILED SPRINGS BY A HIGH-FREQUENCY MAGNETIC FIELD Joseph L. Calley, Detroit, Mich., assignor to The Murray Corporation of America, Detroit, Mich., a corporation of Delaware Application September 25, 1944, Serial No. 555,744

1 Claim.

This invention relates to a heat treating method, and particularly to a method which continuously advances irregular articles through a magnetic field.

While heretofore in the art articles have been heat treated by placing them in a magnetic field of high frequency, such fields were found to be inadequate to uniformly heat irregular objects such as coil springs, primarily those of a conical and hour-glass type, and especially those having knots at the ends. When such springs were placed in the high frequency magnetic field, the currents induced in the spring were concentrated on particular parts of the spring, such as the coil of the largest diameter and the points where the wire was knotted, resulting in portions of the spring becoming over-heated while other portions were substantially under-heated.

To overcome this difficulty applicant provides a magnetic field of substantial length and passes the springs through the field by rotating them as they are advanced. The field is formed by helically coiling a conductor about a tube made of ceramic or other high heat-resisting insulating materials which are capable of withstanding the heat of the normalizing process. Such materials as porcelain, glass, Micalex, and the like have proven by test to be satisfactory. The conductor is preferably hollow through which water or other coolant is passed to prevent over-heating. The high frequency supply circuit is attached to the ends of the conductor which provides the field for inductively heating the turns of the springs as they are rolled through the field.

A conveyor extends through the insulating tube having spaced insulating elements, each of which engages a spring and advances it therethrough. The inner wall of the tube on which the springs roll is preferably corrugated or otherwise roughened to produce a gripping action on the springs which causes them to rotate as they are advanced by the insulating elements of the conveyor. By controlling the intensity of the field and the speed of the conveyor, the heating of all portions of the spring to a desired normalizing temperature will be uniform by the time a spring passes through the field. It was found that a frequency of substantially one million cycles satisfactorily normalized the springs as they were slowly passed through the tube of a length to contain from six to eight springs.

The conveyor is made up of a plurality of bronze links so as not to become excessively heated by the field when moved therethrough as would occur if such links were constructed of magnetic material. A chute is preferably provided in which the springs may be disposed to be picked up by the insulating elements of the conveyor as they pass through an opening in the tube. Mechanism may be provided for delivering a single spring only to the space between two adjacent insulating elements of the conveyor. The springs may be manually placed the chute or may drop therein directly from the coiling on knotting machines.

Accordingly, the main object of the invention is to roll an irregular magnetic object through an electric field of high frequency for inducing currents into the article which raise the temperature thereof sufficiently to normalize the article.

Other objects and features of novelty of the invention will be specifically pointed out or will become apparent when referring, for a better understanding of the invention, to the following description taken in conjunction with the accompanying drawing wherein:

Figure 1 is a broken view, with parts in section, disclosing a normalizing device embodying features of this invention;

Figure 2 is a reduced plan View of the left-hand end portion of the structure illustrated in Figure l, and

Figure 3 is an end view of the structure illustrated in Figure 1.

A tube I0, made of ceramic material such as clay, glass, Micalex, and the like, has a tube ll of copper or other conducting material helically wound thereon and joined at its ends to conduits 9 which conducts water or other coolant therethrough and to an electric circuit 8. The electric circuit is of the high frequency type in the order of 500,000 to 1,500,000 or more cycles per minute produced by apparatus 1 well known in the art and which is not illustrated or described herein.

A conveyor 12 is supported on spaced pairs of sprocket wheels it which are mounted on shafts 14 in suitable bearings, not herein illustrated, and driven in a suitable manner well known in the art. The conveyor is made up from central links 15 spanned by spaced links l6 interconnected by rods ll, all of which are made of bronze or other nonmagnetic material. Each thread rod ll, as herein illustrated, supports an insulating element !8 and is spaced apart a distance greater than the diameter of the spring or other object to be normalized. The teeth 19 of the sprocket extend within the apertures 2| formed between the links l5 and I6 for driving conveyor at a predetermined speed.

As illustrated in Figur 1, the lower portion 22 of the conveyor passes along the upper inner wall of the tube I0, with the insulating elements l8 extending downwardly toward the bottom wall 23 of the tube. The bottom wall 23 is provided with a plurality of grooves 24 to form an irregular surface for causing the springs 25, or other objects to. be normalized, to be rotated when advanced across the surface by the insulating elements IS. A chute 26 may be employed adjacent to one end of the conveyor from which a spring is delivered between a pair of the insulating elements 18 by which it is advanced through the tube 10. A lever 21' may be employed within the chute in position to be engaged by one of the insulating elements [8 as it is moved through the chute. When the lever 21 is deflected it inserts a holding finger 28 inwardly of the chute to prevent a spring from dropping therethrough until the finger E8 in engagement with the lever 21 passes thereover. When this occurs, the next adjacent finger I8 has advanced sufiiciently to engage the next adjacent spring when it drops from the retracted finger 28 into the chute. The finger 28 assures the delivery of a single spring between each pair of insulating elements 18 as the conveyor advances.

As the conveyor advances through the tube ID, the springs between the insulating elements l8 are rolled across the rough surface of the bottom wall 23 of the tube and produce the rolling of the springs during their advancement. It was found that by rolling an irregular object such as a spring having turns 30, 3| and 32 of difierent diameter, and also having a knot 33- at one or both ends, providing a concentration of metal on the turn 32 of the largest diameter, that all of the portions of the spring would be subjected to the same amount of induced currents so that all portions of the spring would have a uniform temperature rise. The amount of the rise in temperature is controlled by the current, the frequency and the speed with which the conveyor is operated. With the device of the present invention, the springs will pass from the tube 10 seriatim at the proper normalizing temperature in a very rapid manner.

What is claimed is:

The method of normalizing coiled springs made of magnetic material and having at least one coil forming a completed loop which includes the steps: of advancing a plurality of the springs simultaneously through a high frequency magnetic field, and of rotating said springs as they are passed through the field with the axes about which the springs are coiled disposed perpendicular to the path of the magnetic field.

JOSEPH L. CALLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 1,453,358 Kettering May 1,. 1923 2,040,767 Dudley May 12,1936 2,087,731 Klouman July 20, 193.7 2,093,061 Wallace Sept. 14, 1937 2,282,322 Denneen et a1. May 12, 1942 2,291,862 Bailey Aug. 4, 1942 2,325,638 Strickland Aug. 3,. 1943- 2,356,485 Webb Aug, 22,, 194A 

